You can grab this on Bogano, although I can't confirm if the boss counts, so it's best to find one of the regular dudes.
Anyway, when you return to the planet for the story (late game) or if you wanna come back earlier for it, make a run up to the vault and a single oggdo should spawn. At this point, you just gotta wait for his tongue attack. Keep at range and wait for him to open his mouth AND flail his tongue. They've got several different attacks, so it's important to know what to look for. Once you see the move coming, force pull the tongue towards you and hack away. Should pop immediately.
If someone wants to let me know if the boss oggdo on this planet counts, that'd be dope. Happy hunting!